Thermodynamic study of the NaCl+Na2SO4+H2O system by emf measurements at four temperatures

Activity coefficients for sodium chloride in the NaCl + Na2SO4 + H2O ternar y system were determined from emf measurements of the cell Na-glass/NaCl(m(A)), Na2SO4(m(B)), AgCl(s)/Ag at 15, 25, 35, and 45 degrees C and at total ionic strengths from 0.1 to 6 mol-kg(-1). These activity coefficient were analyzed by using the Harned ru le and the treatments of Scatchard-Rush-Johnson and Pitzer. The analysis of activity coefficients at "trace" concentration was also achieved and quali tatively interpreted by considering the ionic interactions that can take pl ace in the mixed system. Finally, the excess Gibbs energy of the mixtures w as calculated and qualitatively analyzed against the composition of the sys tem.